Hybrid electric vehicles (HEV's), plug-in hybrid electric vehicles (PHEV's), battery electric vehicles (BEV's), fuel cell vehicles and other known electrified vehicles differ from conventional motor vehicles in that they are powered by one or more electric machines (i.e., electric motors and/or generators) instead of or in addition to an internal combustion engine. High voltage and high current are typically supplied to the electric machines by one or more batteries that store electrical power.
Electrified vehicles typically employ power supply systems that support bi-directional power flow within the vehicle. The power supply systems include a plurality of switching devices that perform switching operations according to a drive signal produced by a controller to control a load. For example, electrified vehicles often include inverter/converter systems that utilize a plurality of semiconductor switching devices, such as power metal-oxide semiconductor field effect transistors (MOSFET's) or insulated gate bipolar transistors (IGBT's), that selectively undergo switching operations for powering one or more AC drive motors from a DC storage battery, or alternatively, to charge the DC storage battery from an AC source, such as a generator.
An over-voltage event can be caused by various factors, such as voltage-control delay and voltage sensor offset error, and may occur when a switching device of the power supply system undergoes switching operations between ON and OFF. This voltage-spike occurs due to the effect of a large rate of change of current during a switching event, i.e. di/dt, and parasitic inductance L (which can be formulated as V=L·di/dt).
The voltage spike issue described above may become more significant with modern power switching devices, which are generally capable of faster turn-on and turn-off (i.e., large di/dt). Switching power converters are typically designed to include a relatively large voltage margin so that such voltage spike can be maintained below the voltage rating of the switching device. However, in the case of multi-leg switching power converters, such as three-phase PWM inverters commonly used in utility, consumer and automotive applications, simultaneous switching events among two or more legs may lead to relatively large voltage spike across an individual device. This can result in relatively poor voltage rating utilization for multi-leg switching power converters.